Electromagnetic relay



Nov. 2, 1937. 0 STIMSON 2,098,070

ELECTROMAGNETIC RELAY Filed May 29, 1935 Inventor: Allen G. Stimson,

by W a 9M2 His Attorneg. I

a specifically,

Patented Nov. 2, 1937 PATENT OFFICE Allen G. o

General New rivention inagnetizahle ntly a etizable ively l'l accorrl M c nating ancl tnations one: the operating actively to clamp these hfllatlfills, I circuited winding carried the the repulsion force exerted on tea winding opposing the mag- 'orce exerted upon the armature. More 3 provide a supporting bracket formed of magnetizahle material to which apluralityof magnetisahle plates are secured in face-to-iace relation in order to form the magnetizahle frame, the plates the bracket being formed to provide air gap in the frame. Secured to am other portion or? the bracket, is a cantilever spring which resiliently supports the armature in a given position adjacent the magnetizable frame. Resiliently supported for movement with the armature, is a contact arranged to engage a fixed contact when the armature is'attractecl into the air gap. Due to the construction of the armature order e;

orovicie a shortmovahle and the spring, the armature is susceptible notv only to forced vibration within the air gap in accordance with the fluctuation of the magnetic l -l'lshay'nna. N. "3Z0. assignor lternating currezis, hut g are also susceo-tihle when nature is released and ace e31 irregularly i sts a suc til 5 steel or other suit ie ma 'net order to provide for easy assembly o the it on e case, bracket pro varied, with a plurality of fingers or prongs l2 ranged ez'ztentl t ough suitable a thehasac ytwo o -e apertures .te fingers 23 are or sufiacient l en o twardly on opposite sicle the i can the bracket is assembled e groove ii, two straps t5 and ill on opposite side the lease are respectively provided with. aper= tures ll la alignahle Withthe extending ends at the fingers 63. When the bracket and the straps have been assembled on thehase, the extending ends of the fingers '53 may be overturned or otherwise suitably secured to the straps l5 and iii in order to secure the bracket 52 rigidly the base ill. The strap I 6 also serves as an electrical conductor as will be more fully explained hereinafter.

As shown best in Fig. 2, the bracket i2 is provided with a substantially U-shaped portion IS on the opposite sides of which are secured, as for example by the rivets 20, a plurality of simiilarly shaped plates of magnetizable material so as to form a laminated, magnetizable frame 2| having opposed pole faces 22 and 23 forming an air gap at the open end thereof. Mounted on one leg of the magnetizable frame 2| is an operating coil 24 comprising an insulating spool 25 on which the turns of the coil are wound. Ex-

tending outwardly from the leg of the magnetizable frame on which the coil f ll is mounted, is a lug or car 29 formed on the portion l9 of the bracket i2 and arranged to cooperate with the spool 25 to support the coil 26 on the magnetizable frame. The dimensions of the spool are such that when the coil 29 is placed over the leg of the frame 2i and pressed downwardly thereon, the spoolis forced into intimate engagement with the lug ft and with, the corners of the opposite side of the frame leg. Thusa rigid three-point support for the winding 29. is obtained, ,the spool preferably being formed of fiber so' that the lug 29 cuts a groove therein as the coil is forced downwardly on the frame, thereby preventing turning of the coil or vibratory movement thereof.

Formed on the other end of the bracket if, is a supporting portion fl to which. is secured one end of a cantilever spring 28, the other end of which is secured to the legs of a U-shaped armature 29 formed of steel or other suitable magnetizable material. As shown, the spring 29 normally supports the armature 29 in spaced relation with the magnetizable frame 2i so as to form an air gap between the armature and the frame, and the yoke portion 39 of the armature is in alignment with the air gap between the pole faces 22 and 23. Secured to the armature 29 in the air gap between the armature and the frame, I provide a short-circuited winding 3i comprising a single-turn coil of highly conductive material, such as copper, the purpose of which will be more fully described later.

Extending outwardly from the cantilever spring 29 between the legs of the armature 29, is a spring finger, 32 which supports a movable contact in cooperating relation with a fixed contact 36 carried on a supporting post 35 threadedly mounted, as indicated by the reference numeral 99, on the base Hi. This threaded mounting of the .contact post 95 provides for easy adjustment of the relay contacts 93 and 9d.

Extending outwardly from the magnetizable frame 2!! between the legs of the armature 29, is asupporting finger fiil on which is loosely -mounted'a stop bar 99 preferably formed of rawhide or other suitable flexible material As shown, the stop bar 99 is loosely supported intermediate its ends and is thus rendered selfalignable with the armature 29.

In order to describe the operation of the relay, it will be assumed that the relay is connected in the starting and running circuits of a motor in the well-known manner, with the operating coil 26 in series with the running winding and the contacts 99 and 3 3 in series with the starting winding. The external circuit connections will be apparent upon reference to Fig. 4 of Patent- No. 1,996,599 issued April 2, 1935 to Louis W. Thompson, and the internal circuits of the relay will now be traced. The starting winding circuit may be traced from a common terminal of the relay (not shown) which preferably threadedly engages 'an aperture. (Mia) in the strap it, through the strap it, the finger l3 secured thereto, the bracket if, the. cantilever spring 29, the

spring finger 32, the contacts 33 and 36 and the supporting post 95 which is electrically connected to the starting winding of the motor. Likewise,

fl. From the terminal 99 the circuit may be traced through the coil 26 to the terminal ll secured by a terminal screw 62 to a terminal post it which is electrically connected to the running winding of the motor.

It will be apparent now that when the motor (not shown) is connected to a suitable source of alternating-current through the relay, there will be a rush of current through the operating coil 29- which is-connected in the running winding circuit of the motor. The magnetic fiux'produced by energization of the coil 99 will cause the armature to move toward the frame fl and close the contacts 93 and 3A in the starting winding circuit of the motor. It will be seen that this magnetic flux will flow through two parallel paths, the main portion of the flux flowing through the U-shaped magnetizable frame 2i and the air gap between the pole faces 22 and 23, thereby creating a high intensity magnetic field between the pole faces, and the remainder of the magnetic flux passing through the bracket if, the cantilever spring 29, the magnetizable armature 29 and the air gap between the armature and the frame fl. Accordingly, the armature 29 will be attracted toward the magnetic frame not only by the fiux fiowing through the gap between the armature and the frame but also by the leakage flux between the pole faces 22 and 23.

As the armature 29 approaches the high intensity magnetic field between the pole faces 22 and 23, the magnetic attractive force on the armature greatly increases, this force varying substantially inversely as the square of the distance between the high intensity region and the armature. Accordingly the armature moves with a quick action to close the contacts 39 and 34!, and it will be observed that by reason of the resilient mounting of the armature f9 and the contact 93, and by reason of the fact that the armature in its attracted position does not rigidly engage the magnetizable frame fl or any other stationary member, the relay is substantially noiseless.

As shown, the. pole faces 22 and provide a relatively wide region of high intensity magnetic fiux within which the armature may come to rest, and the pole face 222 is preferably beveled in order to provide a component of flux at an angle to the main flux between the poles. it will be understood that since the main flux between the poles is substantialy parallel with the armature when the armature is in its attracted position a state of comparativeinstability may exist between'the retractive force exerted by the spring 29 and the magnetic force exerted on the armature. However, the component of flux produced by the beveled face of the pole 22 exerts a steadying pull on the armature, which tends to maintain the armature in a position of equilibriumwithin the air gap.

As hereinbefore mentioned, the armature and the spring 29 are ofrelatively light construction and consequently, the armature has a tendency to vibrate in-the gap between the pole faces 22 and 29 as the alternating-current excitation varies from a zero .to a maximum value during each half-cycle. The short-circuited winding iii,

however, which is secured to the armature and in part tothe repulsion force, exerted thereon by the magnetic field, which force is in a direction to oppose the magnetic pull on the armature, and in part to the out-ot-phase flux produced by the circulating current which is induced in the short-circuited winding. A substantial portion or this out-oI-phase flux, which is substantially 90 out of phase with the'main flux, passes through the magnetizable frame 2| and through the armature 29 between the pole faces 22 and. 23, and since this flux will obtain "a maximum value when the main flux is passing 3 through its minimum value, the magnetic pull exerted on the armature by this out-oI-phase fins: tends to stabilize the armature.

as soon contacts 33 and 34 are closed, motor begins to accelerate and as the motor eomes up to the current through the run o motor may rea h the desired starting winding is deenergized, ""5951 retain its armature in energizi g cur a raise substantiail necessary r tir The manner in edition Wes this differential operat 'e-"mso i observing "e Wi the resilient nearly to plain the e operati n of the the air ap will con id emitted. Will be rd deenergized and the arm nly released for operation out of the spring 28, the kinetic energy ature it is moved will be one armature beyond normal position, and kinetic energy will then be stored the spring 28. When sufiicient energy has been stored in the spring to bring the armato rest, spring will be eifective to return the armature towards the normal position and again the armature will move through the nor inal position and will store energy in the spring. Thus it will be seen that the armature and the spring when once released from the air gap, will vibrate freely about the normal position with a natural periodicity and amplitude of vibration which is dependent upon the moment of inertia of the armature and the strength of the spring.

This free vibration or the armature is not only objectionable from the standpoint of noise but the amplitude of vibration may be suflicient to n and through the coil 2 decreases.

cause the contacts 33 and 34 to be reclosed each time that the armature vibrates.

Accordingly, I have provided the stop bar 38 arranged to engage the armature 28 as it moves out of the air gap and absorb the kinetic energy of the armature. Preferably the stop 38 is arranged slightly beyond the normal position oi. the armature in order to minimize the load on the spring when the relay is deenergized. However, it will be apparent that the stop must be arranged closely enough to the normal position of the armature to prevent an appreciable amount of energy being stored in the spring. Likewise I have found that if the stop is located too close to the magnetizable frame 2%, the armature 28 will have a tendency to vibrate each time that the energizing cin'rent in the coil 24 passes through. the maxirnmn value during each cycle. 4 It will or" course be understood that some cases the free vibration o the armature may not be of su.i=

such cases the stop be omitted,

rill be apparen relay to a y when d frequency cairn,

own a particular embodiment of my invention, ill be nnderstood, course, I no not to be limited thereto since many r be made 3, therefore, contemplate by a ended claims to sever any such modifications fall within the true spirit and a scope of my invention.

What I cla l as new and desire to secure by Letters Patent oi the United States, is:

3.. An alternatlngwurrent relay comprising a magnetizable frame having an air gap, 9. magnetizable armature, a cantilever spring secured to said armature for normally supporting said armature in a position adjacent said frame, said armature and said cantilever spring having a natural amplitude of vibration about said normal position when said armature is moved from said position to stress said spring and then released, means including an operating winding for producing a magnetic flux in said frame to attract said armature from said normal position to a V o v Jill position within said air gap, means including a short-cirouited winding carried by said armature for damping forced vibration of said armature within said air gap, and a stop for preventing free vibration of said armature about said normal position when said armature is released from said air gap, said stop being positioned beyond said normal position but within the natural vibration range of said armature.

2. An alternating-current relay comprising a magnetizable frame having an air gap, a magnetizable armature, a cantilever spring secured to said armature for normally supporting said armature in a position adjacent said frame, said armature and said cantilever spring having a natural amplitude of vibration about said normal position when said armature is moved from said position to stress said spring and then released, means including an operating winding for producing a magnetic flux in said frame to attract said armature from said normal position to a position within said air gap, means including a short circuited winding carried by said armature for damping forced vibration of said armature within said air gap; and a stop for absorbing the kinetic energy of said armature to prevent free vibration about said normal position when said armature is released from said air gap, said stop being formed of resilient material and being positioned within the natural vibration range of said armature.

3.- An alternating-current relay comprising a magnetizable framehaving an air gap, an operating winding associated with said frame energizable to provide a' high intensity magnetic field in said air gap, a magnetizable armature normally resiliently positioned adjacent said air gap and movable into said air gap in response to the magnetic force exerted due to a predetermined degree of energization of said winding, said armature having a natural amplitude of vibration about its normal position when released from said air gap, means including a short-circuited Winding carried by said armature for damping forced vibration of said armature within said air gap, the repulsion force exerted on said short-circuited winding opposing the magnetic force on said armature, said armature substantially closing said air gap when in its attracted position whereby an increased force is exerted on said armature to maintain said armature in said air gap until the energization of said operating winding is reduced below said predetermined value, and stop means for preventing free vibration of said armature upon release of said armature from said air gap.

4. An alternating-current relay comprising a magnetizable frame having an air gap, an operating winding associated with said frame and energizable to provide a magnetic field of high in tensity in said air gap, a magnetizable armature, a cantilever spring for normally supporting said armature in a position adjacent said air gap, said armature being arranged to be attracted into said high intensity magnetic field upon a predetermined degree of energization of said winding against the biasexerted by said cantilever spring, the force on said armature increasing as said armature enters said air gap whereby said armature is maintained in said high intensity field until the energization of said operating winding is reduced below the value required for initial operation of said armature, means including a short-circuited winding for damping forced vibration of said armature within said air gap, said cantilever spring operating said armaaooaoro ture and said short-circuited winding out of said air gap upon said reduction of energization of said winding, and a stop for absorbing the kinetic energy of said armature to preventfree vibration about said normal position when said armature is moved out of said air gap by said cantilever spring.

5. An alternating-current relay comprising a magnetizable "supporting bracket having a U- shaped portion, a plurality of U-shaped magnetizable plates secured to said U-shaped portion of said bracket in face-to-face relation to form a laminated frame having an 'open end, a U shaped magn'etizable armature, a cantilever spring, means securing one end of said spring to another portion of said bracket and the other end of said spring to the legs of said U-shaped armature, the yoke portion of said armature being normally positioned adjacent the open end of said laminated frame, means including an operating winding on said frame for operating said armature from said normal position to a position in which the yoke portion of said armature nests between the legs of said laminated frame, a finger extending outwardly from one leg of said frame between the legs of said armature, and stop means carried by said finger for limiting the movement of said armature away from said frame under the influence of said cantilever spring upon a decrease in the energization of said operating winding.

6. A relay comprising a U-shaped magnetizable frame, a lJ-shaped magnetizable armature, means for resiliently supporting said armature substantially at right angles to said frame with the *yoke portion of said armature in alignment with the gap between the legs of said U-shaped frame, said yoke portion being normally positioned outwardly from the ends of said frame legs, means including an operating winding associated with said frame energizable to operate said armature to a position in which said yoke nests between the legs of said frame, one of said frame legs nesting within said armature, said resilient supporting means being efiective to move said armature away from said-frame upon a decrease means, the ends of said bar extending into the path of movement of the legs of said armature.

7. An alternating-current relay comprising a laminated magnetic frame having a plurality of substantially rectangular poles, an inner lami-- nation of said frame having a portion extending outwardly from a side of one of said poles, an operating coil for said relay comprising a spool of insulating material surrounding said one pole, the dimensions of said extending portion being such that when said coil is pressed onto said pole, said spool is forced into intimate engagement with said extending portionand with the remote corners of said rectangular pole whereby a rigid three-point support for said coil is provided.

8. An alternating-current relay comprising a magnetizable supporting bracket .having a U- shaped portion, a plurality of U-shaped magnitizable plates secured on opposite sides of said IU-shaped bracket portion in face-to-face relasaid 1202a, said spool is forced inm intimate engageoh said ear with the remote cemem 1203a ts provide a rigid tiree-poimt 60 3 3 01 said amend 1g cuawardly 

